Modular power supply with plural rectifier housings back of which contains rectifying devices, a transformer and fan means

ABSTRACT

A modular power supply for converting three-phase alternating current to direct current for high kva applications. A plurality of individual rectifying modules are all fed through a common three-phase SCR controller. Each module in turn comprises a delta-wye transformer and a three-phase, full wave diode rectifying circuit. An individual cooling fan is packaged with the transformer and rectifying circuit of each module in a confined package. The transformer in each module is fed from the common SCR controller to an individual circuit breaker associated with each module but separately packaged in the module bank immediately adjacent its associated module. The DC output from each module is collected by a common bussing arrangement and a particular automatic voltage-current regulator is provided to control the duty cycle of the common SCR controller. The modules are arranged in a compact bank by stacking the modules in vertical columns and providing a plurality of columns side by side.

United States Patent Koltuniak et al.

[ 1 Feb. 8, 1972 [54] MODULAR POWER SUPPLY WITH PLURAL RECTIFIERHOUSINGS BACK OF WHICH CONTAINS RECTIFYING DEVICES, A TRANSFORMER ANDFAN MEANS [72] lnventors: Michael A. Koltuniak, Warren; Thomas N.

Urquhart, Troy, both of Mich.

[731 Assignee: Controlled Power Corporation, Fannington, Mich.

[22] Filed: Feb. 6, 1970 [21] Appl. No.: 9,331

[56] References Cited UNITED STATES PATENTS Winograd Storsand ..321/8 CRECTIFIER 3,241,034 3/1966 Ludwig ..32l/8C 3,390,321 6/1968 Plow..32l/l8X Primary Examiner-William M. Shoop, Jr. Attorney-Dames,Kisselle, Raisch & Choate ABSTRACT A modular power supply for convertingthree-phase alternating current to direct current for high kvaapplications. A plurality of individual rectifying modules are all fedthrough a common three-phase SCR controller. Each module in turncomprises a delta-Wye transformer and a three-phase, full wave dioderectifying circuit. An individual cooling fan is packaged with thetransformer and rectifying circuit of each module in a confined package.The transfonner in each module is fed from the common SCR controller toan individual circuit breaker associated with each module but separatelypackaged in the module bank immediately adjacent its associated module.The DC output from each module is collected by a common bussingarrangement and a particular automatic voltage-current regulator isprovided to control the duty cycle of the common SCR controller. Themodules are arranged in a compact bank by stacking the modules invertical columns and providing a plurality of columns side by side.

10 Claims, 9 Drawing Figures m 3Q DC IFIER RECTlFlER PAIENTEUFEB 8 m2SHEET 1 OF 4 3-1'6. 2 MICHAEL A. KOLTUNIAK THOMAS N.URQUHART BYATTORNEYS PATENTED FEB 8 I972 SHEET 2 0F 4 a a a a w w a M Q VII w A m 6a 4 f 3 6 A 6 6 Z 4 4% M FM w :9 4h MM 5% l w w \J fw M W 3 M ii ii ITiiINVENTORS F163 MICHAEL A. KOLTUNIAK BY THOMAS N. URQUHART ATTORNEYSPATENTEDFEB we 3.641.419

SHEET a UF 4 220 rrn WK zw 12 E UJJ INVENTORS MICHAEL A. KOLTUNIAKTHOMAS N.URQUHART BZMAM ATTORNEYS MODULAR POWER SUPPLY WITH PLURALRECTIFIER HOUSINGS BACK OF WHICH CONTAINS RECTIFYING DEVICES, ATRANSFORMER AND FAN MEANS Among the objects of the present invention areto provide an altemating-to-direct current converter that providesreliability, flexibility, expandability and simplicity for different DCpower requirements; that is constructed to simplify shipping, handling,installation and repair; that provides effective cooling while operatingunder widely varying ambient conditions and eliminating cooling airfiltration for many applications; that is compact and lightweight bycomparison to prior DC power supplies for the same kva rating; thateffectively utilizes a plurality of individual rectifying units ormodules in a wide variety of DC power applications; that provides aneffective yet simple automatic voltagecurrent regulation for a pluralityof individual modules without requiring individual control of eachmodule; and that is capable of isolating the failure at an individualmodule while permitting continued operation of remaining modules tothereby prevent a total failure of the power supply.

Other objects, features and advantages of the present invention willbecome apparent in connection with the following description, theappended claims and the accompanying drawings in which:

FIG. I is a front elevational view of an altemating-to-direct currentconverter having a modular construction according to the presentinvention consisting of 21 individual modules;

FIG. 2 is a functional block diagram for a modular power supply of thepresent invention and is illustrated for only three modules for purposesof simplicity;

FIG. 3 is a schematic circuit diagram for the maincontroller-transformer-rectifying circuit paths of the power supplyillustrated in FIG. 2;

FIG. 4 is a schematic circuit diagram showing the details of avoltage-current regulation circuit of FIGS. 2 and 3;

FIG. 5 is a top plan view of a single module used for high voltageapplications;

FIG. 6 is a side view of the module illustrated in FIG. 5;

FIG. 7 is an exploded fragmentary view of one side of the moduleillustrated in FIG. 5;

FIG. 8 is a fragmentary perspective view illustrating a complete moduleand its associated circuit breaker; and

FIG. 9 is an enlarged fragmentary view from FIG. 1 illustrating a singlemodule and its associated circuit breaker.

Referring more particularly to FIG. 1, there is illustrated a modularpower supply of the present invention generally comprising a bank 32 of21 individual rectifying modules 34 and a cabinet 35 which houses thecontroller circuits for the bank of modules. The 21 modules are arrangedin three vertical columns, each column consisting of seven modules.Associated with each module is a separate circuit breaker 36. Each ofthe individual modules 34 is substantially identical, both in mechanicalconstruction and electrical circuitry. Similarly, for purposes ofunderstanding the present invention utilizing a plurality of modules,supplied from a common input bus and supplying a common output bus, itwill be apparent that the operation and construction is basically thesame regardless of the number of modules 34 utilized. Hence for purposesof illustration, the functional block diagram of FIG. 2 illustrates asimplified modular power supply incorporating only three modules,designated 34a, 34b and 340. For purposes of clarity, the correspondingcircuit breakers 36a, 36b, 360 are illustrated enclosed in the dashedline indicating an individual module, although it will be understoodthat the circuit breakers 36 are physically separated from otherelectrical components in the associated module 34 as will later bedescribed in greater detail.

Referring more particularly to FIG. 2, a three-phase source 40 isconnected by lines 42 through a main circuit breaker 44 to a three-phaseSCR controller 46. The output of controller 46 is in turn fed viaparallel paths through the respective modules 34a-c to the common DCoutput busses 48., 50. Each of the parallel paths. through a respectivemodule 34a, 34b,

DC feedback control signal from the voltage-current regulation circuitindicated generally at 62. The control signal at 60 controls the angularposition of the various gating signals from circuit 58 relative to thephase angles of the positive and negative half cycles in each of thethree phases at controller 46. Stated differently, the control signal 60determines the duty cycle in each of the phases at controller 46 tothereby regulate the power supplies to the modules 34.

In general, the DC control signal at 60 is derived from either a voltagelevel at busses 48, 50 or the current level at busses 48, 50. Moreparticularly, the voltage across busses 48, 50 is applied through asuitable isolating resistor 66 across a summing resistor 68 to developthe output signal at the summing terminal 70 that forms one inputterminal of the NOR-gate 72. A voltage reference from source 74 is alsoapplied through an isolating resistor 76 across summing resistor 68 andin bucking relation to the feedback voltage through resistor 66 suchthat the output signal developed at the summing terminal 70 has a valueindicating whether the reference is greater or less than the feedbackfrom busses 48, 50 in addition to indicating the amount of deviationtherebetween. Similarly, the output current in the positive bus 50 issampled by the shunt 80 and the current feedback signal is fed through aDC amplifier 82, achopper 84, an output driver amplifier 86 to arectifier-filter circuit 88 that develops a DC signal representing themagnitude of the current in'lines 48, 50. The signal developed bycircuit 88 is applied through an isolating resistor 90 across a summingresistor 92. Equal portions 90a,

90b, 90c of resistor 90 are arranged to be shorted by respectivecontacts 94a, 94b, 94c. Contacts 94a, 94b, 94c are operated by therespective circuit breakers 36a, 36b, 36c so that whenthe circuitbreakers are closed their corresponding contacts 94 are opened. As willlater be explained in greater detail, should one of the circuit breakersopen, for example, circuit breaker 36a, the corresponding contact 94awill be closed to short out resistor 90a and increase the feedbackapplied to the summing resistor 92 from the shunt 80. A currentreference signal from source 98 is also applied across the summingresistor 92 through an isolating resistor 100 in bucking relation to thecurrent feedback signal from circuit 88 so that the output developed atthe summing terminal 102 has an amplitude that indicates which of thetwo signals exceeds the other as well'as the amount of differencebetween the signals applied across resistor 92. The signal developed atthe summing point 102 is applied to the other input of the NOR"-gate 72.

The circuit details of the SCR controller 46, the modulesv 34, togetherwith start-stop circuitry and the fan motor circuitry for cooling themodules 34 is shown in greater detail in FIG. 3 whereas the circuitdetails of the voltage-current regulating circuits 62 are shown ingreater detail in FIG. 4. Referring more particularly to FIG. 3, thethree-phase lines 42 are fed through the circuit breaker 44 to the SCRcontroller 46. Each of the three-phase lines is connected to the circuitbreakers 36 through a pair of silicon controlled rectifiers 1 10, 111for one of the lines, 111' for a second of the lines and 110", 111" forthe third line. Since the construction and operation of a three-phase,full wave duty cycle controller is known, per se, for purposes ofsimplicity only one of the SCRs important aspect of the presentinvention, the controller 46 is effective to simultaneously control thepower applied through the respective circuit breakers 36a, 36b, 360 tothe primary winding l14a-c of the three transformers 52a-c. It should benoted that transformers 52 have their primaries 114 connected in a deltaand their secondaries 116 wye connected in the preferred embodiment. Ithas been found with the modular circuit being described, a delta-deltatransformer and a wyewye transformer do not operate as efiectively for agiven physical size due to poorer transformer efficiencyflt has alsobeen found that a Wye-delta transformer creates phasing problems at theSCR controller 46. The secondaries 116 feed the rectifying circuits 54,each of which consists of six diode rectifiers connected in thethree-phase, full wave bridge circuit illustrated.

The start-stop circuit 120 is fed from one phase of the threephase inputat lines 42 via a control transformer 122 which steps down the 480 voltsacross the single-phase input to l volts for the circuit 120. Connectedacross the secondary of transformer 122 is a pilot light 124. A controlrelay RLM is arranged to be connected across the secondary oftransformer 122 through a normally closed stop switch 126 and a normallyopened start switch 128. Relay RLM has two normally open contacts lRLMand 2RLM. When start switch 128 is closed to energize relay RLM, thecontacts ZRLM close to seal relay RLM and contacts IRLM close to providethe power for the regulating circuit 62 which includes the SCR firingcircuit 58 and for the fan motors 130 that cool the SCRs in thecontroller 46. For purpose of simplicity, in the present application, acontrol relay is designated by a letter designationand the contactsoperated by that relay will be designated by the same letter designationpreceded by a numeral designation. Substantially the same conventionwill be utilized for identifying solenoids and the contacts associatedtherewith. A separate pilot light 134 is connected across relay RLM toprovide a separate indication that the' power to the circuit 62 is on. a

A solenoid .CBM is also arranged to be connected across the secondary oftransformer 122 by'an emergency stop switch 136. Solenoid CBM is part ofthe circuit breaker 44 and is arranged to open the main circuit breaker44 in response to closure of the emergency stop switch 136.

Two of the main lines 42 also feed a second stepdown control transformer140 which is arranged to energize the circuit 142 that controls themotors for respective fans in each of the modules 34. Circuit 142 isalso arranged to disconnect a module in response to excessivetemperatures at the heat sink for the diode rectifiers 54. Moreparticularly, a control relay RLA connected directly across thesecondary of transformer 140 has a normally closed contact lRLA in thecircuit 120. When transformer 140-is energized to in turn energize relayRLA, contacts lRLA open so that a time delayed closing of contacts lRLMdoes not cause solenoid CBM to be energized.

If, however, the power to circuit 142 is lost, as by a fuse blowing,relay RLA is deenergized and contacts lRLA close to energize solenoidCBM through the contacts lRLM that are closed in response toenergization of relay RLM. This operates to open the main circuitbreaker 44 to disconnect the entire power supply 30 from the lines 42.When the main circuit breaker 44 is opened by the solenoid CBM, eitherby operation of the emergency stop switch 136 or closure of contactslRLA and lRLM, the power to the power supply 30 can be reconnected onlyby manual closure of the main circuit breaker 44.

The circuit 142 also includes fan energizing and temperature overloadcircuits 144a, l44band 1440 for the modules 34a, 34b, 34c, respectively.Since the circuits 144 are substantially identical, an understanding ofthe construction and operation of these circuits will be apparent from adescription of one of the circuits 144a. The circuit 144a includes acontrol relay RLla arranged to be connected across the secondary oftransformer 140 through anormally opened contact 1CB1 that ismechanically linked with the contacts of the main circuit breaker 36a inthe module 34a so that when the contacts in 36a are closed, the contacts1CB1 are also closed to energize relay'RLla. Relayv RLla has a normallyopen contact lRLla and a normally closed contact 2RLla (FIG. 3,designated by numeral 940 in FIG. 2). Closure of contact lRLla energizestwo fan motors 148 (FIGS. 3 and 5) that are housed in the module packagefor the module 34a. Energization of motors 148 via contacts lRLla isthrough a current responsive element 150a that is physicallyincorporated in the circuit breaker 36a of the module 34a so that inresponse to excessive current through the element 150a the circuitbreaker 36a is opened to disconnect the transformer 52a from the SCRcontroller 46. To this end, a normally open, temperatum-responsivebimetal contact 152a is connected in series with a current limitingresistor 154a across the fan motors 148. Bimetal 1520 is mounteddirectly on the heat sink for the diodes in the bridge rectifier 540 sothat in response to excessive temperature at the diode the bimetal 152acloses to parallel resistor 154a with motors 148 causing the currentthrough element 1500 to increase to the point where it causes circuitbreaker 36a to open. As previously indicated in connection with thedescription of FIG. 2, the contacts 2RLla (FIG. 3,

designated 94a in FIG. 2) are normally closed but in response toenergization of relay RLla contacts 2RLla open so that resistor 90a isinserted in series with the current feedback from shunt 80 to decreasethe feedback applied across the summing resistor 92. Similarly, shouldcircuit breakers 36b or 36c open due to excessive current through theinput to the respective primaries 114b, 1140, the corresponding contact2RLlb or 2RL1c will close to short the corresponding resistor b. or 90 cto further increase the current feedback to the summing resistor 92. Inthis regard, it should be noted that each of the circuit breakers 36includes at least two current responsive elements (not shown) each ofwhich is connected in a different one of the input lines to the deltaconnected primary 114, i.e., in series with a respective line, so thatthe current sensing element opens the circuit breaker 36 in response toexcessive current in any of the input phases to the transformer 52.Hence as indicated earlier, if the circuit breaker 36 is opened, eitherdue to manual positioning of the circuit breaker or due to openingthereof in response to excessive current in the primary 114a, acorresponding resistor 90a will be shorted.

FIG..3 also shows the specific construction of the wye-wye transformer59 through which the SCR firing circuit 58 is energized. Transformer 59is utilized to convert a three-wire input to a four-wire output with thefourth wire providing a false neutral in the SCR firing circuit 58. Theuse of the false neutral in the secondary of transformer 59 assures thatall six SCRs 1'10, 111 in the controller 46 fire in the desired sequenceindependent of phase rotation of the three-phase source 40.

Referring now in greater detail to the circuit diagram for thevoltage-current regulation circuit 62 illustrated in FIG. 4, the circuit62 is energized by the input at lines 132, 133 (FIGS. 3 and 4) from thestart-stop circuit (FIG. 3). The alternating current input is rectifiedat and the DC output from rectifier 170 is applied across a pair ofpotentiometers 172, 174 through a series regulator indicated generallyat 176 to provide a stable reference voltage across the potentiometers172, 174. Potentiometer 172 has a wiper 178 that serves as the currentreference source (98, FIG. 2), with wiper 178 being connected throughresistor 100 to the summing pointl02. The summing point 102 is alsoconnected through the serially connected resistors 90a, 90b, 90c and viathe line 180 to the output of the rectifier-filter circuit 88. As waspreviously noted, the current feedback signal from shunt 80 (throughamplifier 82, chopper 84, amplifier 86 and rectifier and filter circuit88, FIG. 1) is applied in bucking relationship to the reference signalfrom wiper 178. Hence it will be apparent that for a positive increasein the DC output current across shunt 80, the feedback signal appliedacross summing resistor 92 increases in a negative direction. The outputsignal developed across resistor 92 is applied to one-half of the NORgate circuit 72 which generally comprises a two-stage buffer amplifierformed by transistors 182, 183, the output of which drives the base ofthe transistor 184.

Similarly, the potentiometer 174 has a wiper 185 that serves as thevoltage reference source (74, FIG. 2) to supply the voltage referencethrough resistor 76 to the summing point 70. The summing point 70 isalso connected through the resistor 66 and a suitable filter 186 to thenegative bus 48 via lead 188. For purposes of simplicity, filter 186 isomitted from FIG. 2 and it will be understood that filter 186 merelysmooths the ripples in the DC output developed across busses 48, 50 aswell as serving as a voltage divider to set the level of the voltagefeedback to the summing point 70. As indicated earlier, the voltagefeedback signal via resistor 66 bucks the reference voltage from wiper185 so that an increase in the voltage across busses 48, 50 results in anegatively increasing signal being applied to the summing point 70. Theoutput developed across resistor 68 is applied to the NOR-gate 72through a buffer amplifier formed by two transistors 192, 193, theoutput of which drives the base of transistor 194. Transistors 184, 194have a common emitter-resistor 196 that develops a differential outputsignal in a manner to be described in greater detail. The output acrossresistor 196 is fed through an operational amplifier 200 to the controlinput 60 of the SCR firing circuit 58. As previously indicated, the SCRfiring circuit 58 may be of generally conventional construction. Inresponse to a variation in the level of the output signal developed atinput 60, corresponding equal shifts in the firing angle of all six SCRs110, 111 is achieved. In the preferred embodiment, the SCR firingcircuit was a Vectrol full wave phasetrol," Model No. VPH1019-230/460-3X3, heretofore sold commercially by the Sprague ElectricCompany, North Adams, Massachusetts. Amplifier 200 is primarily to matchthe output signal developed across resistor 196 with the firing circuit58 so that the firing angle of the SCRs 110, 111 can be varied oversubstantially a full 175 in response to the variations developed acrossoutput resistor 196.

The operation of the voltage-current regulation circuit 62 will bebetter understood assuming that there is initially no load on the sixSCRs 110, 111 and that the voltage reference at wiper 185 is set toregulate the DC output voltage at busses 48, 50 to 12 volts. Thereference voltage at wiper 185 is compared against the voltage feedbackvia line 188 which is initially zero at the summing point 70. Hence thepositive reference causes the emitter-follower 192 to be forward biasedand this drives transistor 194 into conduction. The transistor 194 isone-half of the NOR-gate 72 formed by transistors 184, 194. Transistor194 develops an output signal across resistor 196 which is fed toamplifier 200 to in turn develop a DC control signal at 60 which drivesthe SCR firing circuit. The magnitude of the signal at 60 varies theeffective width of the SCR gate pulses which, in turn, controls the SCRconduction angle. As the conduction angle of the six SCRs increases, themagnitude of the output voltage at 48, 50 will increase developing anincreasing feedback voltage across the output 48, 50 and this in turn isfed back via resistor 66 and compared at resistor 68 against the voltagereference from 185. The voltage feedback is negative relative to thepositive reference and hence when compared with the reference signal,the difference signal varies the base drive at transistor 194 toregulate the output at the constant 12 volts, regardless of line andload conditions. Regulation in a constant voltage mode continues untilthe amplified current feedback signal becomes large enough to turntransistor 184 on. In the absence of a load current or until the loadcurrent reaches a maximum value as determined by the setting of thecurrent reference wiper 178, the base of transistor 184 is reversebiased and transistor 184 remains off. As a result, only voltage controlis exercised by transistor 194. However, when the output current atbusses 48, 50 has reached a value which is sufficiently large that thefeedback from shunt 80 when compared with the current reference signalat wiper 178 turns transistor 184 on, conduction at transistor 184 turnstransistor 194 off via the common emitter resistor 196 and crossoverfrom voltage control to current control occurs. Further increases inoutput current result in a greater negative feedback that interacts withthe current reference signal at resistor 92 so that constant current ismaintained. During constant current control, the voltage is free tofall, Stated differently, when crossover from constant voltage controlto constant current control occurs, theSCRs are phased back to a shorterduration conduction angle so that current through the load remainsconstant, even though more current is demanded. By the same token, whenthe device is in the constant voltage mode as opposed to constantcurrent, if the load were constant and the line or the load were tochange such that the voltage tried to increase, the voltage would bedecreased.

As previously indicated, the current feedback is efiected throughresistors a, 90b, 900, each of which is tied in with its respectivemodule 34a, 34b, 34c; that is, the resistors 90a, 90b, 90c are arrangedto be shorted by respective contacts 2RLla, 2RL1b, 2RL1c so that thefeedback level is inversely proportional to the number of operativemodules. By way of further illustration, for a 2l-module system, therewill be 21 resistors in series with the current feedback and eachresistor is shorted by a normally closed relay contact. When each moduleis energized by closing its associated circuit breaker 36, this, inturn, opens a normally closed relay contact 94, thereby inserting aresistor. As a result, the number of resistors that are active in thecurrent feedback network represent the number of modules that are inoperation. In the event that a module 34 becomes inoperative as a resultof a failure mode or manual disconnect, this in turn reactivates a relaycontact 94 to short out the resistor 90 that represents that module inthe current feedback network. As a result, the current feedback signalis increased, thereby setting the automatic control to the point atwhich the full load current must be limited in order not to exceed thecapability of the remaining modules active in the system. This systemhas particular merit in a system capable of n modules 34 but where only2n/3 modules 34 are installed in the system, which leaves n/3 modulesthat are not operable at that time. The circuit breakers 36 for theassociated n/3 modules are left open. Using a normally closed relaycontact to shunt a resistor prevents exceeding the current capability ofthe remaining 2n/3 modules that are in the system. When other of the n/3modules are added and activated by closing their circuit breakers, thecontacts corresponding to contacts 94 are opened, thereby altering thecurrent feedback signal and allowing the system to deliver the fullcurrent capability as reflected by the increased number of modules. Thelevel of the current feedback will determine the maximum current outputat busses 48, 50, even though the wiper 178 is set for a greater currentthan the active modules are capable of producing.

The mechanical construction of the power supply 30 together with theconstruction of the individual modules 34 is better illustrated in FIGS.5-9 wherein a plurality of horizontally disposed U-shaped channels 210are mounted on vertical uprights 212. Each of the modules 34 has a pairof bottom corner extrusions 214 having laterally outwardly projectingintegral flanges 216 slideable on the top face of an associated channel210. The flanges 216 and channels 210 extend the full length of themodules 34. Each of the bottom comer extrusions 214 are mounted onopposite ends of a pair of lower transformer brackets 217. Each bracket217 has a downtumed flange on its outer end that is fastened on anupstanding leg 218 of the comer 214 by one of the screws 220, Similarly,upper comer extrusions 230 are mounted on opposite ends of a pair ofupper transformer brackets 232 by means of the upturned flanges on theends of brackets that are fastened on downwardly depending legs 234 ofthe upper comer extrusions 230 by screws 220'. The laminations of thecore 238 of the transformer 52 are securely bolted together between theupper transformer brackets 232 and the lower transformer brackets 217.The transformer primary winding 114 and secondary winding 116 are woundon core 238 in a generally conventional manner. Hence the transformerand its mounting brackets 217, 232 rigidly support the corner extrusions214, 230, the lower corner extrusions 214 in turn providing a slideablemount on the channel 210 so that the modules 34 can slide outwardly fromthe frame members 212. The sides of the module 34 are each closed by avertical side panel 240 which is fastened on the integral legs 218, 234of the bottom and top comers 214, 230, respectively, by the fourtransformer mounting screws 220, 220' and four additional screws 242. Aflat top panel 246 is removably carried in grooves on the upper comerextrusion 230 whereas a lower bottom panel 248 is removably carried ingrooves on the bottom corner extrusions 214. Front and rear grills 250,252, respectively, are mounted on opposite ends of the module 34 byscrews threaded in the corner extrusions. The mounting screws 242 at therear end of the modules 34, the right side as viewed in FIGS. and 6,also support a fan bracket 254 that carries the two fan motors 148(FIGS. 3 and 5) for each of the modules 34.

The six diode rectifiers and the rectifying circuit 54 are mounted on asuitable heat sink 260 which in turn is mounted on a heat sink bracket262. Bracket 262 extends transversely of the module 34 and is fastenedat opposite lateral sides thereof to the bottom corner 214 by the lowerfront screws 242. The positive bus 48' and the negative bus 50' connectthe output of the rectifying circuit 54 to the main bus lines 48, 50with the busses 48', 50' extending from the rectifying circuit 54rearwardly through the module 34 and outwardly through one of the sidepanels 240 to suitable connectors at the rear of the modules where it isparalleled with the output from the other modules 34.

The particular construction of a single module described hereinabove hasseveral important advantages. For purposes of illustration, the module34 described in connection with FIG. 5 is for a high voltage rectifiersystem utilizing the heat sink construction 260 illustrated in FIG. 5.Similarly, the output in a high voltage rectifying system may be byconventional high tension bus leads 48, 50'. However, when the modularpower supply 30 is constructed for low voltage systems, many of the samestructural components can be used, namely, the corner extrusions 214,230, the same top panel 246, the same bottom panel 248, the front andrear grills 250, 252 and the fan bracket 254 and fan motors 148. Ingeneral, the principal difference then between a high voltage and lowvoltage module merely involves a different mounting arrangement for alow voltage, high current heat sink and a slightly different transformerthat is slightly larger but generally on the same order of dimensions asthe transformer illustrated in FIG. 5 for the high voltage system. Inthe preferred embodiment of a low voltage system, the side panels 240are modified so that the side panel serves not only as a structuralcomponent but also as a low voltage bus bar and, to some extent, servesto further conduct heat away from the low voltage heat sink.

It is also important that the various parts of each module are, to someextent, interchangeable. Hence the two bottom comers 214 have identicaltransverse cross sections and can be cut from the same extrusion.Similarly, the two upper corners 230 have identical transverse crosssections and are cut from the same extrusion. The top and bottom panels246, 248 are identical and the four transformer brackets 217, 232 areidentical. Although the front grill 250 is preferably of a differentconstruction than the rear grill 252, the front grill on a high voltagepower supply is interchangeable with the front grill on a low voltagepower supply. Additionally, the modules 34 for either a high voltageapplication or a low voltage application have the same outsidedimensions.

As noted hereinabove, the transformer brackets 232, 217 extendtransversely substantially the full width of the module 34 and provide amain structural component giving rigidity to the module. Hence in thepreferred embodiment, the transformer brackets 232, 217 are made ofheavy gauge steel whereas the comers 214, 230 are extruded aluminum andthe top, bottom and side panels are aluminum sheet metal. The grills250, 252 are molded plastic. Hence the' majority of the weight of anindividual module is in the core 238 and the windings 114, 116. At leastas important is the fact that each individual module 34 can be removedfrom the power supply 30 so that the modules can be handled, transportedand installed individually to complete the assembly on site. This hasnumerous advantages over a bulky, heavy power supply providing the samekva output and contained in a single package. By way of example, a24-volt module weighs approximately 234 pounds and a frame for 21modules weighs approximately 2,500 pounds, whereas for a high voltagesystem at 300 volts utilizes modules each weighing 225 pounds with a2l-module frame weighing approximately 2,450 pounds.

The control circuitry described in connection with FIGS. l-4 achieveseffective control of plural modules made under close productiontolerances to provide mechanical and electrical uniformity as betweendifferent modules. Similarly, the construction described hereinabove canprovide mechanical and electrical symmetry in the different phases of anin-,

dividual module. In this regard, the reactance of the transformer 52 isthe most single important factor in determining how the current isshared as between parallel modules as well as between diodes within therectifying circuit 54 of a given module. Hence variations due todifferences between diodes and the rectifying circuits 54 are ofsecondary importance as compared to the transformer 52.

The horizontal airflow pattern through each of the individual modulesalso offers several distinct advantages, including a relatively largeinlet at the front grill 250 for each individual module as well as alarge combined total area for all of the modules when assembled in abank such as the 21- module bank shown in FIG. 1. The cooling air isdrawn by the fans located at the rear of the module so that the cool airfirst cools the heat sinks, such as the heat sink 260, and then thetransformers before being exhausted at the rear of the module to grill252. Again each of the individual grills on a single module offers arelatively large exhaust area as well as a combined exhaust area for theplurality of modules assembled in a bank. The flow from front to rear,as contrasted to vertical flow means that the cooling air is likely tobe cleaner as contrasted to a system having an inlet at only a low leveladjacent the floor. With a rear exhaust, it is not necessary to have asubstantial clearance at the top of the power supply 30. Also with thelarge inlet and outlet areas for the cooling air, large quantities ofair can be moved at a relatively low velocity, producing a much quieteroperating system by comparison to prior art devices.

Important advantages of the modular power supply described hereinaboveare that a complete power supply can be built up from inventory modulesto meet practically any power requirement by using the proper number ofmodules. A customer anticipating large future power requirements neednot purchase the entire power supply to service those futurerequirements but by buying a large cabinet and using less than themaximum number of modules, the customer can meet present powerrequirements and then add additional modules as his demands increase.The system is very reliable in that extra modules may be kept on hand bythe customer to eliminate down time in the event of a failure at one ofthe modules. The defective module is merely left in place and itscircuit breaker opened while the circuit breaker on the spare module isclosed. A self-adjusting voltage and current control with current limitsoverride according to the number of modules in operation, and indeed theparticular modules that are active, facilitate this flexibility andreliability of the modular power supply.

By way of further disclosure, the total capacity of the modular powersupply 30 of the type described hereinabove is determined primarily bythe ratings of the SCRs 110, 111 in the SCR controller. The ratings onair cooled SCRs presently available commercially are such that, in thepreferred embodiment, the total kw. output from the power supply 30 ison the order of 500 kw. After extensive development, it has been foundthat the above total kw. output can be achieved while maintainingadequate safety ranges. Moreover, it has been found by extensivedevelopment that the above maximum output capabilities can be achievedmost effectively by using 28 separate modules 34, for example, fourvertical columns of seven modules per column. This particulararrangement provides a very compact power supply having a large ultimatepower capability.

We claim:

1. An alternating to direct-current converter for large powerapplications comprising a plurality of individual rectifying unitsconnected together to be responsive to a common source of alternatingvoltage and to develop a common direct current output, power controlmeans operatively coupled between said source and said plurality ofrectifying units, each of said rectifying units comprising at least arespective transformer having a primary winding and a secondary winding,a respective rectifying circuit coupled in the output of said secondarywinding and a respective circuit breaker means operatively coupled incircuit with said transformer means to selectively connect anddisconnect its associated transformer to said power control means, andwherein each of said rectifying units further comprises a respectivehousing extending longitudinally in a generally horizontal direction andbeing constructed to define a confined path for airflow through saidhousing in a horizontal direction, an inlet at one end of said housing,an outlet at the other end of said housing and fan means mounted in eachhousing and adapted to establish a moving current of air through saidhousing along said path, a respective transformer and rectifying circuitbeing mounted in each housing so as to be disposed in said movingcurrent of air.

2. An alternating to direct current converter for large powerapplications comprising a frame adapted to accommodate and support aplurality of substantially identical rectifying units, a plurality ofrectifying units mounted in and supported by said frame, said rectifyingunits being electrically connected together to be responsive to a commonsource of alternating voltage and to develop a common direct currentoutput, power control means operatively coupled between said source andsaid rectifying units, regulator means responsive to said common outputand operatively coupled to said power control means to vary the powerfrom said source to said rectifying units in accordance with variationsin said common output, and a plurality of circuit breaker means each ofwhich is operatively coupled between said power control means and arespective rectifying unit for selectively connecting and disconnectingits respective unit to and from said power control means, and whereineach of said rectifying units further comprises a modular housing havingwall means defining a substantially confined path through said housingfor cooling air, a cooling air inlet at one end of said housing, anoutlet at the other end of said housing, fan means mounted in saidhousing and adapted to establish a current of moving air through saidhousing from the inlet thereof to the outlet thereof, a respectivetransformer mounted in each housing so as to be disposed in said path ofcooling air therethrough and having a primary winding and a secondarywinding, said primary winding being adapted to be electrically coupledto said power control means through a respective circuit breaker means,and a respective rectifying circuit mounted in said housing so as to bedisposed in said path of cooling air therethrough and being electricallycoupled between said secondary winding and said common output.

3. The converter set forth in claim 2 wherein said common source is athree-phase source and said power control means comprises at least threepairs of rectifiers, at least one of said rectifiers in each of saidpairs being a controlled rectifier having a control electrodeoperatively coupled to said regulator means to vary the power from saidsource in accordance with variations in said common output.

4. The converter set forth in claim 2 wherein said frame has a pluralityof openings extending horizontally through said frame from the front ofsaid frame to the rear of said frame and wherein each modular housing isremovably mounted in a resspective opening of said frame.

. The converter set forth in claim 4 wherein said frame openings aregenerally rectangular, each housing extends longitudinally in ahorizontal direction through said frame and has a transverse verticalcross section that is generally rectangular, each housing has asubstantially closed top wall, a sub stantially closed bottom wall andsubstantially closed sidewalls, said top, bottom and sidewalls definingsaid path for cooling air through said modules, an inlet grill at afront end of each housing and an outlet grill at the rear end of eachhousing so that said path for cooling air is a substantially directhorizontal path from said inlet grill through said housing, over saidtransformer and said rectifying circuits, to said outlet grill.

6. The converter set forth in claim 4 wherein each circuit breaker meansis mounted on said frame directly adjacent a respective opening in whichan associated modular housing is supported.

7. The converter set forth in claim 4 wherein a first plurality ofopenings in said frame are arranged in a first vertical column, a secondplurality of openings in said frame are arranged in a second verticalcolumn with each opening in said second column in horizontal,side-by-side alignment with a respective opening in said second column,a first plurality of said modular housings supported in said frameopenings in said first column and a second plurality of said modularhousings supported in said frame openings in said second column.

8. The converter set forth in claim 2 wherein said rectifying circuitsare mounted adjacent said inlet of their respective housings, said fanmeans are mounted adjacent said outlets of their respective housings,and said transformers are mounted in their respective housings betweensaid fan means and said rectifying means.

9. The converter set forth in claim 1 wherein said rectifying circuitsare mounted adjacent said inlet of their respective housings, said fanmeans are mounted adjacent said outlets of their respective housings,and said transformers are mounted in their respective housings betweensaid fan means and said rectifying means.

10. A modular rectifying unit for use in an altemating-todirect currentconverter having a plurality of such units, said rectifying unitcomprising a housing having a substantially closed top wall, asubstantially closed bottom wall and substantially closed sidewalls, anair inlet at one end of said housing, an air outlet at the other end ofsaid housing, said walls extending longitudinally of said housing anddefining a direct, generally straight line path from said inlet to saidoutlet for cooling air circulating through said housing, fan meansmounted in said housing adjacent said outlet and adapted to establish acurrent of moving air along said path through said housing, rectifyingdevices mounted in said housing adjacent said inlet so as to be disposedin said cooling airpath and a transformer mounted in said housinglongitudinally thereof between said rectifying devices and said fanmeans, said transformer having a secondary winding electricallyconnected to said rectifying devices.

23 323 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION.

Patent No. 3,641,419 Dated February 8, 1972 Inventor) MICHAEL A.KOLTUNIAK and THOMAS N. URQUHART It is certifiedthat error appears inthe above-identified patent and that said LettersPatent are herebycorrected as shown below: 7

In the Title [two occurrences: (l) on information cover page; (2) at thebeginning of Column I], delete "BACK" and insert in place thereof--EACH.

In-Colufnn 8, line 46, before "advantages" delete "Important" and insertin place thereof --Other important--.

Signed and sealed this 18th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETGHER,JR. ROBERT GOTTSCHALK Commissioner of PatentsAttesting Officer zg gg I UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION.

Patent No. 3,641,419 Dated F r ary 72 Inventor(s) A. and N.

It is certified that error appears in the above-identified patent andthat said LettersPatent are hereby corrected as shown below:

In the Title [two occurrences: (l) on information cover page; (2) at thebeginning of Column 1], delete "BACK" and insert in place thereof--EACH-.

In'ColumnB, line 46, before "advantages" delete "Important" and insertin place thereof --Other important--.

Signed and sealed this 18th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I ROBERT GOTTSGHALK Commissioner of PatentsAttesting Officer

1. An alternating to direct-current converter for large powerapplications comprising a plurality of individual rectifying unitsconnected together to be responsive to a common source of alternatingvoltage and to develop a common direct current output, power controlmeans operatively coupled between said source and said plurality ofrectifying units, each of said rectifying units comprising at least arespective transformer having a primary winding and a secondary winding,a respective rectifying circuit coupled in the output of said secondarywinding and a respective circuit breaker means operatively coupled incircuit with said transformer means to selectively connect anddisconnect its associated transformer to said power control means, andwherein each of said rectifying units further comprises a respectivehousing extending longitudinally in a generally horizontal direction andbeing constructed to define a confined path for airflow through saidhousing in a horizontal direction, an inlet at one end of said housing,an outlet at the other end of said housing and fan means mounted in eachhousing and adapted to establish a moving current of air through saidhousing along said path, a respective transformer and rectifying circuitbeing mounted in each housing so as to be disposed in said movingcurrent of air.
 2. An alternating to direct current converter for largepower applications comprising a frame adapted to accommodate and supporta plurality of substantially identical rectifying units, a plurality ofrectifying units mounted in and supported by said frame, said rectifyingunits being electrically connected together to be responsive to a commonsource of alternating voltage and to develop a common direct currentoutput, power control means operatively coupled between said source andsaid rectifying units, regulator means responsive to said common outputand operatively coupled to said power control means to vary the powerfrom said source to said rectifying units in accordance with variationsin said common output, and a plurality of circuit breaker means each ofwhich is operatively coupled between said power control means and arespective rectifying unit for selectively connecting and disconnectingits respective unit to and from said power control means, and whereineach of said rectifying units further comprises a modular housing havingwall means defining a substantially confined path through said housingfor cooling air, a cooling air inlet at one end of said housing, anoutlet at the other end of said housing, fan means mounted in saidhousing and adapted to establish a current of moving air through saidhousing from the inlet thereof to the outlet thereof, a respectivetransformer mounted in each housing so as to be disposed in said path ofcooling air therethrough and having a primary winding and a secondarywinding, said primary winding being adapted to be electrically coupledto said power control means through a respective circuit breaker means,and a respective rectifying circuit mounted in said housing so as to bedisposed in said path of cooling air therethrough and being electricallycoupled between said secondary winding and said common output.
 3. Theconverter set forth in claim 2 wherein said common source is athree-phase source and said power control means comprises at least threepairs of rectifiers, at least one of said rectifiers in each of saidpairs being a controlled rectifier having a control electrodeoperatively coupled to said regulator means to vary the power from saidsource in accordance with variations in said common output.
 4. Theconverter set forth in claim 2 wherein said frame has a plurality ofopenings extending horizontally through said frame from the front ofsaid frame to the rear of said frame and wherein each modular housing isremovably mounted in a respective opening of said frame.
 5. Theconverter set forth in claim 4 wherein said frame openings are generallyrectangular, each housing extends longitudinally in a horizontaldirection through said frame and has a transverse vertical cross sectionthat is generally rectangular, each housing has a substantially closedtop wall, a substantially closed bottom wall and substantially closedsidewalls, said top, bottom and sidewalls defining said path for coolingair through said modules, an inlet grill at a front end of each housingand an outlet grill at the rear end of each housing so that said pathfor cooling air is a substantially direct horizontal path from saidinlet grill through said housing, over said transformer and saidrectifying circuits, to said outlet grill.
 6. The converter set forth inclaim 4 wherein each circuit breaker means is mounted on said framedirectly adjacent a respective opening in which an associated modularhousing is supported.
 7. The converter set forth in claim 4 wherein afirst plurality of openings in said frame are arranged in a firstvertical column, a second plurality of openings in said frame arearranged in a second vertical column with each opening in said secondcolumn in horizontal, side-by-side alignment with a respective openingin said second column, a first plurality of said modular housingssupported in said frame openings in said first column and a secondplurality of said modular housings supported in said frame openings insaid second column.
 8. The converter set forth in claim 2 wherein saidrectifying circuits are mounted adjacent said inlet of their respectivehousings, said fan means are mounted adjacent said outlets of theirrespective housings, and said transformers are mounted in theirrespective housings between said fan means and said rectifying means. 9.The converter set forth in claim 1 wherein said rectifying circuits aremounted adjacent said inlet of their respective housings, said fan meansare mounted adjacent said outlets of their respective housings, and saidtransformers are mounted in their respective housings between said fanmeans and said rectifying means.
 10. A modular rectifying unit for usein an alternating-to-direct current converter having a plurality of suchunits, said rectifying unit comprising a housing having a substantiallyclosed top wall, a substantially closed bottom wall and substantiallyclosed sidewalls, an air inlet at one end of said housing, an air outletat the other end of said housing, said walls extending longitudinally ofsaid housing and defining a direct, generally straight line path fromsaid inlet to said outlet for cooling air circulating through saidhousing, fan means mounted in said housing adjacent said outlet andadapted to establish a current of moving air along said path throughsaid housing, rectifying devices mounted in said housing adjacent saidinlet so as to be disposed in said cooling airpath and a transformermounted in said housing longitudinally thereof between said rectifyingdevices and said fan means, said transformer having a secondary windingelectrically connected to said rectifying devices.